Even if D.C. Mayor Vince Gray triumphs in the multi-candidate Democratic primary April 1, he would still have to overcome a prominent, independent opponent in the general election in November to win a second term.

D.C. Council member David Catania (I-At Large), who is well-known to voters after winning five straight citywide elections, told me Friday that there was “an extraordinarily high probability” that he would challenge Gray if the mayor emerged as the Democratic nominee.

Catania formed an exploratory committee this month for a possible mayoral race. But he had not said before that he planned to run if Gray were the opponent.

The council member’s comments increase the likelihood that the battle for mayor will last until November. Typically, the mayoral campaign effectively ends when Democrats pick their candidate in a city whose politics they dominate.

Catania, a 45-year-old lawyer, would have to overcome quite a few obstacles to win. He would be the first non-Democrat and first white to be elected mayor since the city achieved home rule. He would need to convince voters that he could be effective despite having what he concedes is a quick temper.

D.C. Council member David Catania (I-At Large), who is well-known to voters after winning five straight citywide elections, told me Friday that there was “an extraordinarily high probability” that he would challenge Vincent Gray if the mayor emerged as the Democratic nominee. (Sarah L. Voisin/The Washington Post)

He also would have to convince the electorate that he could deliver on his promises to do far better than Gray or his predecessor, Adrian Fenty, to improve public schools. Catania emphasized that education is his No. 1 priority, but both Fenty and Gray said the same.

Still, Catania might stand a better chance of toppling Gray than any of the mayor’s Democratic primary opponents. The anti-Gray vote is sure to be divided among the four council members and at least two other credible candidates on the ballot in April’s primary.

By contrast, Catania and Gray would probably run head-to-head in the general election.

“In a crowded field, [Gray] stands a pretty good chance of getting a plurality,” Catania said in an interview. But he predicted that the mayor could not get a majority one-on-one, because polls show that too many voters are disillusioned over the scandal in the mayor’s 2010 campaign.

“The die is cast,” Catania said. “In the court of public opinion, when there’s enough evidence to suggest that people no longer trust you and don’t view you as a person of integrity, I think that’s very hard to reverse.”

Catania declined to say what he would do if a Democrat other than Gray won the primary. It’s safe to assume he would study the results and decide whether he had a good chance of winning.

Any race would be a gamble, because it would require him to give up the council seat he has held for 16 years.

Catania hopes to impress voters with his education expertise and advocacy of far-reaching legislation to accelerate school reforms.

In his first 11 months as chairman of the council’s education committee, he has visited nearly half of the city’s schools. He champions measures to reduce truancy, increase spending on low-income schools and curb “social promotion” of unqualified students to a higher grade. He said he thought he can overcome the stigma of being an independent and, until 2004, a Republican.

“If you’re running as an unknown commodity as an independent in a heavily Democratic city, that definitely presents a challenge,” Catania said. “But I’ve won more citywide races than everybody else in the race combined, so I’m a known commodity.”

Such confidence notwithstanding, Catania’s victories came with a caveat: He didn’t have to compete against Democrats because two seats on the council are reserved for candidates outside the majority party.

Catania said most voters today would disregard his race in judging him.

“You look at Detroit — that’s 80 percent African American. It just elected a white mayor. There’s ample evidence that people look past race,” he said.

Catania acknowledged his difficulties with anger management. He can be sarcastic and cutting in comments at council meetings and in news media interviews. But he said the problem has receded.

“I will be the first to confess on more than one occasion my passion has gotten the better of me,” Catania said. “As I’ve aged in this position — I was 29 when I was first elected — I think I’ve become more measured. But every once in a while, I relapse.”

The mayoral race is so fluid now that it’s hard to know what role Catania will ultimately play. But his readiness to run adds a sizable bump to Gray’s potential path to reelection.